Yunseop Choi (POSTECH)

Jongcheol Seo (POSTECH)

Yunseop Choi (POSTECH)

Junyoung Ahn (POSTECH)

Jongcheol Seo (POSTECH)

^​ Lithium ion is one of the most important ions in both chemistry and our daily life, particularly due to its central role in lithium-ion batteries. In such systems, the solvation complex of the ion significantly influences ion transport behavior, thus, understanding its solvation properties and structural characteristics is essential. Diamines bind effectively with lithium ions, and their coordination complexes are employed in a variety of chemical reactions, highlighting the importance of studying their binding behavior.

In this work, we investigated (Li⁺I⁻)_nLi⁺ cluster ions solvated with ethylenediamine and tetramethylethylenediamine (TMEDA) using electrospray ionization–ion mobility spectrometry–mass spectrometry (ESI–IMS–MS). The solvation affinities of various alkali halides were examined, with LiI in combination with TMEDA exhibiting the highest affinity. Cluster ions such as Li⁺I⁻Li⁺·(diamine)₂​ and (Li⁺I⁻)₃Li⁺·(diamine)₃ were observed with high abundance, and their structures were analyzed using IMS. Interestingly, while DFT calculations indicated that the most thermodynamically stable structure involves all diamines coordinating in a bidentate fashion, experimental results revealed the presence of bridging diamine configurations. The calculations further suggest that these bridging structures may be kinetically trapped during the ESI process.

 This study provides new insights into the solvation behavior of alkali halide clusters and offers guidance for the effective design of ligands for chemical and electrochemical applications, including battery technologies.